Many disciplines use the total body fat values or body composition values of individuals. These disciplines may for example include epidemiology, where the aim is to find the various factors relating to body composition and fat values of a specimen representative of groups of individuals and determine the occurrence, frequency, method of spread and evolution of diseases affecting these groups of individuals.
Moreover, these concepts of body fat or composition may also be used within the context of establishing or monitoring specific diets, or body remodeling, for the general public (services available over the Internet or in beauty parlors) or for paramedical or medical personnel. Teams of practitioners are in particular specializing in the monitoring of high-level sportsmen.
There are several techniques for determining a person's total body fat. Some of these techniques are analyzed in the document by H. C. Lukaski “Methods for the assessment of human body composition: traditional and new” (Amer. J. Clin. Nutr. 1987, 46, 537-56). The measurement obtained by dual-photon absorptiometry, also called DEXA (Dual Energy X-ray Absorptiometry) provides very reliable results and is a reference method for total body fat and for body composition. It consists in irradiating the person with a beam of photons having two different energies, and it makes it possible to distinguish absorption by the various tissues and to calculate their mass. However, it has the drawback of requiring the person being measured to be irradiated with a low dose of X-rays and of being able to be carried out only in hospital.
Moreover, medical resonance imaging or MRI allows the body fat to be determined in as many of the person's sections as planes of sections made during the examination. It is then possible from these measurements in the planes of section to estimate the total body fat. This technique is described for example in the document by T. S. Han, I. E. Kelly, K. Walsh, R. M. E. Greene and M. E. J. Lean, “Relationship between volumes and areas from single transverse scans of intra abdominal fat measured by magnetic resonance imaging” (Int. J. Obes. 1997, 21, 1161-1166). However, the procedure is lengthy and the equipment required is expensive. This technique, which can only be carried out in a hospital, is not suitable for routine examinations owing to the extent of the means employed.
There are also techniques that can be implemented away from hospitals and require less expensive equipment than the DEXA or MRI methods. Among these, mention may be made of the skinfold caliper method, which consists in firmly taking hold of a fold of skin and in determining, from the thickness of the fold and from mathematical equations, the body fat. However, this determination technique is subject to errors during measurement by the operators. Furthermore, in particular it is not valid for the obese.
Moreover, document U.S. Pat. No. 5,941,825 (“Measurement of body fat using ultrasound methods and devices” by Stephan Gramp, Philipp Lang and John Mendlein) describes a technique for determining a person's total body fat using the same principle as that presented by Jackson and Pollock in 1978 using the skinfold caliper method, who determined by using a formula, the percentage total fat by means of fat thickness measurements taken in the arms, chest, abdomen, back and thighs. Document U.S. Pat. No. 5,941,825 employs a novel formula and a fat thickness measurement principle based on ultrasound.
According to document U.S. Pat. No. 5,941,825, the local subcutaneous fat thickness is measured using an ultrasound device at 11 points. These points correspond to the following respective regions: medial calf; lateral calf; anterior thigh; posterior thigh; triceps; biceps; chest; abdomen; axilla; subscapular region; and suprailiac region. A fat volume is then deduced on the basis of these eleven local fat thickness values using a formula, and this estimated volume is multiplied by a fat density in order to determine the total body fat.
This technique has the advantage of being able to be carried out in nonmedical establishments. However, it does require a relatively lengthy measurement step, since it involves eleven points. Moreover, a comparative study of the results provided by this method and those provided by the DEXA reference technique highlights appreciable differences.